Step 1: Thoroughly wash all canning jars, lids, and bands in hot, soapy water. Rinse well. Keep jars hot (in simmering water or a warm oven) until ready to fill. Place new lids in a small saucepan of simmering (not boiling) water to soften the sealing compound.
Step 2: Wash peaches. To easily peel, prepare a large pot of boiling water and a large bowl of ice water. Immerse 3-4 peaches into boiling water for 30-60 seconds, until skin starts to wrinkle.
Step 3: Immediately transfer blanched peaches to the ice water bath to stop cooking. Once cool enough to handle, use a paring knife to slip off the skins.
Step 4: Halve peaches and remove pits. If desired, slice halves into quarters. To prevent browning, place cut peaches in a bowl of water with a splash of lemon juice or ascorbic acid solution while you prepare the rest.
Step 5: Prepare the syrup: In a large pot, combine 6 cups water with 2 cups sugar for a light syrup (adjust sugar for desired sweetness). Heat over medium-high, stirring until sugar dissolves. Bring to a gentle boil, then reduce heat and keep warm.
Step 6: Remove a hot jar from the canner or oven. Place a canning funnel on top. Pack peaches tightly into the hot jars, leaving 3/4-inch headspace.
Step 7: Add 1 tablespoon of bottled lemon juice to each quart jar (or 1/2 tablespoon to pint jars).
Step 8: Carefully ladle the hot syrup over the peaches, ensuring they are completely covered. Maintain 1/2-inch headspace (the space between the syrup and the rim of the jar).
Step 9: Use a bubble remover tool or a clean non-metallic utensil to remove any trapped air bubbles. Gently press peaches to release bubbles. Add more hot syrup if needed to restore 1/2-inch headspace.
Step 10: Wipe the rim of the jar thoroughly with a clean, damp cloth to remove any sticky residue, ensuring a proper seal.
Step 11: Center a hot lid on the jar, then screw on a band until fingertip tight (just until resistance is met, do not overtighten).
Step 12: Carefully place filled jars onto the rack in your water bath canner. Ensure jars are not touching each other. Add more hot water if needed, ensuring water covers jar tops by 1-2 inches.
Step 13: Cover the canner and bring water to a rolling boil. Once boiling, begin timing: Process pint jars for 20 minutes, quart jars for 25 minutes. Adjust processing time for altitude if necessary (consult a reliable canning guide).
Step 14: After processing, turn off heat, remove canner lid, and let jars stand in hot water for 5 minutes.
Step 15: Using a jar lifter, carefully remove hot jars and place them on a clean towel on your countertop, spaced apart. Do not disturb for 12-24 hours.
Step 16: After cooling, check for seals. The center of the lid should be concave and not flex when pressed. Remove screw bands, wash jars, label with contents and date, and store in a cool, dark place.